I. Field of the Invention
This invention relates generally to solid fuel burning furnace systems, and more specifically to the construction of a heat exchanger for use therein.
II. Discussion of the Prior Art
In my copending U.S. Pat. No. 4,201,187, filed Sept. 8, 1978, and entitled "Modular Solid Fuel Furnace System", I describe in detail the construction of a solid-fuel burning furnace system of the type in which the heat exchanger of the present invention finds use. As is set out in that patent application, the heat exchanger comprises a plurality of horizontally extending tubes which are effectively divided into first and second sets by means of suitably placed baffles. The tubes are supported at each end by means of spaced apart vertically extending support plates having apertures formed therethrough for receiving the ends of the heat exchanger tubes. The heat exchanger is positioned within the furnace cabinet such that hot, smoke laden gases are drawn from the firebox, through a first set of the plurality of tubes in a first direction and through the second set in the opposite direction and from there through the flue and chimney. A clean-out door is provided in the cabinet to provide access to a first end of each of the tubes whereby soot and creosote like deposits could be periodically scraped from the inside surfaces of the heat exchanger tubes.
Clean air to be heated is made to pass over the exterior surfaces of the first and second sets of tubes comprising the heat exchanger. To avoid "cross-talk" between the hot, smoke laden and potentially lethal gases flowing through the interior of the heat exchanger tubes and the clean forced air to be circulated through the building to be heated, it had been necessary to form a 360.degree. weld at the intersections of each of the heat exchanger tubes and the support plates through which these tubes pass. Such a welding process, being somewhat labor intensive, added significantly to cost of the furnace system. Thus, a need existed for a heat exchanger construction which could eliminate the need for the 360.degree. seam weld without jeopardizing the safety of the occupants of the building utilizing the system.
The present invention comprises an improvement over the heat exchanger construction disclosed in the aforereferenced patent application. By creating a buffer zone between the front heat exchanger support plate and the rear surface of the clean-out box, the possibility for the aforementioned "cross-talk" is eliminated without the need for a weld extending completely around the perimeter of the heat exchanger tubes at their intersections with the front support plate and the rear surface of the clean-out box. Only a tack weld at predetermined points along the perimeter are necessary, these tack welds serving to hold the support plate and clean-out box relative to the heat exchanger tubes passing therethrough.